Extended access class barring (EAB), is used today to handle overload situations in cellular communication systems. These overload situations can occur where mobile devices connected to the cellular communication system require data services in excess of what can be supported by the cellular communication system at a given time. EAB functions via mobile devices that are connected to cellular communication system and are configured to support EAB. The mobile devices are grouped into N different ‘access classes’ where the percentage of mobile devices will be approximately the same for the subset of access classes used to support normal priority mobile devices. There may also be a subset of access classes used to support higher priority mobile devices which may represent a relatively small percentage of the overall mobile devices supported by the cellular communication system (these mobile devices and their corresponding access classes are not further discussed herein). Each of the access classes corresponding to normal priority devices can be separately “barred” from accessing the cellular communication system and thereby prevented from requesting resources for either voice or data communication from base stations and similar components of the cellular communications system.
As different groups of mobile devices (i.e. one or more access classes) are prevented from accessing the cellular communication system resources, the cellular communication system can decrease the load on itself, and thereby prevent the system from being overloaded. In other words, the cellular communication system is able to block subsets of the connected mobile devices from using the system resources according to their assigned access class, which staggers the load on the system over time as the mobile devices in the barred access classes must wait until their respective access classes are no longer barred from accessing system resources at which point in time other access classes are likely to be barred. For example, if 10 access classes are used to support all mobile devices (normal priority) then each of these access classes would represent about 10% of the total number of mobile devices in which case the network would bar 20% of them by setting EAB content to indicate that any 2 of these access classes are barred.
EAB is controlled by broadcasting a so called EAB mask via the base stations of the cellular communication system. The EAB mask indicates which access classes are barred at a given time. This broadcast of the EAB mask occurs periodically. For example, in global systems for communication (GSM) or enhanced data rates for GSM evolution (EDGE) networks it is broadcast at least once every eight seconds and when acquired by a mobile device it will not be re-acquired for another 30 seconds. In other words, for a mobile device connected to an GSM/EDGE base station, the nominal refresh interval for system information is 30 seconds. Further, the EAB mask provides a coarse quantization in steps of 10% (i.e., the system can bar 10%, 20%, up to 100%) of all mobile devices supporting EAB.
Any subset of mobile devices that have received the same EAB mask will continue to apply that same EAB mask until the next time the mobile device refreshes its system information (i.e. once barred as a result of reading the same EAB mask all the subset of mobile devices will become synchronized as they will utilize the same future instance of the EAB mask to update their EAB mask and thereby determine if their accesses are still barred). This can result in the case where one or more previously barred access classes are determined to be “un-barred” at the same point in time (i.e., when multiple currently barred mobile devices read the same future EAB mask and thereby determine they are no longer barred) so that there can potentially be a large number of mobile devices making simultaneous access to the cellular communication system, which in turn can cause an overload situation. This overload can also arise as a result of the synchronized mobile devices saving (instead of deleting) the payload associated with each barred access attempt experienced during the 30 second system information refresh period (i.e., once a mobile device determines that it is barred it still retains the uplink payload that triggered the access attempt in the hope that it can be still be transmitted at a future point).